Mirror Surface Finishing of Silicon Wafer Edge Using Ultrasonic Assisted Fixed-Abrasive CMP (UF-CMP)
Yongbo Wu*, Weiping Yang**, Masakazu Fujimoto*,
and Libo Zhou***
*Department of Machine Intelligence and Systems Engineering, Akita Prefectural University, 84-4 Tsuchiya-ebinokuchi, Yurihonjo, Akita 015-0055, Japan
**Jiangxi Agricultural University, Economic Development District, Nanchang, Jiangxi 330045, China
***Ibaraki University, 4-12-1 Nakanarusawa, Hitachi, Ibaraki 316-8511, Japan
This paper proposes a new method of using Ultrasonic Assisted fixed-abrasive CMP (UA-CMP) to treat silicon wafer edges. In this method, a disc-shaped pellet containing CeO2 abrasives is attached to the end face of an ultrasonic head. The head is elliptically vibrated at an ultrasonic frequency, rotated at a given speed, and pressed against the work-surface of a silicon wafer edge at a certain normal force. In so doing, a solid-state chemical reaction occurs between the CeO2 abrasives and the silicon to form amorphous Ce-O-Si, which is easily removed from the silicon by the mechanical action of the ultrasonic vibration and rotation of the pellet. An experimental apparatus is produced and its fundamental performance is confirmed experimentally. Subsequently, the optimal processing conditions are determined experimentally using the Taguchi method. A mirror edge surface of around Ra3nm with few defects is obtained repeatedly under the optimum conditions.
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